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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package channel provides the implemention of channel-based data-link layer
// endpoints. Such endpoints allow injection of inbound packets and store
// outbound packets in a channel.
package channel
import (
"context"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
"gvisor.dev/gvisor/pkg/tcpip/stack"
)
// PacketInfo holds all the information about an outbound packet.
type PacketInfo struct {
Pkt tcpip.PacketBuffer
Proto tcpip.NetworkProtocolNumber
GSO *stack.GSO
}
// Endpoint is link layer endpoint that stores outbound packets in a channel
// and allows injection of inbound packets.
type Endpoint struct {
dispatcher stack.NetworkDispatcher
mtu uint32
linkAddr tcpip.LinkAddress
GSO bool
// c is where outbound packets are queued.
c chan PacketInfo
}
// New creates a new channel endpoint.
func New(size int, mtu uint32, linkAddr tcpip.LinkAddress) *Endpoint {
return &Endpoint{
c: make(chan PacketInfo, size),
mtu: mtu,
linkAddr: linkAddr,
}
}
// Close closes e. Further packet injections will panic. Reads continue to
// succeed until all packets are read.
func (e *Endpoint) Close() {
close(e.c)
}
// Read does non-blocking read for one packet from the outbound packet queue.
func (e *Endpoint) Read() (PacketInfo, bool) {
select {
case pkt := <-e.c:
return pkt, true
default:
return PacketInfo{}, false
}
}
// ReadContext does blocking read for one packet from the outbound packet queue.
// It can be cancelled by ctx, and in this case, it returns false.
func (e *Endpoint) ReadContext(ctx context.Context) (PacketInfo, bool) {
select {
case pkt := <-e.c:
return pkt, true
case <-ctx.Done():
return PacketInfo{}, false
}
}
// Drain removes all outbound packets from the channel and counts them.
func (e *Endpoint) Drain() int {
c := 0
for {
select {
case <-e.c:
c++
default:
return c
}
}
}
// InjectInbound injects an inbound packet.
func (e *Endpoint) InjectInbound(protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) {
e.InjectLinkAddr(protocol, "", pkt)
}
// InjectLinkAddr injects an inbound packet with a remote link address.
func (e *Endpoint) InjectLinkAddr(protocol tcpip.NetworkProtocolNumber, remote tcpip.LinkAddress, pkt tcpip.PacketBuffer) {
e.dispatcher.DeliverNetworkPacket(e, remote, "" /* local */, protocol, pkt)
}
// Attach saves the stack network-layer dispatcher for use later when packets
// are injected.
func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
e.dispatcher = dispatcher
}
// IsAttached implements stack.LinkEndpoint.IsAttached.
func (e *Endpoint) IsAttached() bool {
return e.dispatcher != nil
}
// MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
// during construction.
func (e *Endpoint) MTU() uint32 {
return e.mtu
}
// Capabilities implements stack.LinkEndpoint.Capabilities.
func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
caps := stack.LinkEndpointCapabilities(0)
if e.GSO {
caps |= stack.CapabilityHardwareGSO
}
return caps
}
// GSOMaxSize returns the maximum GSO packet size.
func (*Endpoint) GSOMaxSize() uint32 {
return 1 << 15
}
// MaxHeaderLength returns the maximum size of the link layer header. Given it
// doesn't have a header, it just returns 0.
func (*Endpoint) MaxHeaderLength() uint16 {
return 0
}
// LinkAddress returns the link address of this endpoint.
func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
return e.linkAddr
}
// WritePacket stores outbound packets into the channel.
func (e *Endpoint) WritePacket(_ *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt tcpip.PacketBuffer) *tcpip.Error {
p := PacketInfo{
Pkt: pkt,
Proto: protocol,
GSO: gso,
}
select {
case e.c <- p:
default:
}
return nil
}
// WritePackets stores outbound packets into the channel.
func (e *Endpoint) WritePackets(_ *stack.Route, gso *stack.GSO, pkts []tcpip.PacketBuffer, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
payloadView := pkts[0].Data.ToView()
n := 0
packetLoop:
for _, pkt := range pkts {
off := pkt.DataOffset
size := pkt.DataSize
p := PacketInfo{
Pkt: tcpip.PacketBuffer{
Header: pkt.Header,
Data: buffer.NewViewFromBytes(payloadView[off : off+size]).ToVectorisedView(),
},
Proto: protocol,
GSO: gso,
}
select {
case e.c <- p:
n++
default:
break packetLoop
}
}
return n, nil
}
// WriteRawPacket implements stack.LinkEndpoint.WriteRawPacket.
func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error {
p := PacketInfo{
Pkt: tcpip.PacketBuffer{Data: vv},
Proto: 0,
GSO: nil,
}
select {
case e.c <- p:
default:
}
return nil
}
// Wait implements stack.LinkEndpoint.Wait.
func (*Endpoint) Wait() {}
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